It is known to display a remaining charging time by using a map showing a relationship between the battery capacity accumulated in the battery and the battery terminal voltage to identify a battery capacity (SOC) that is charged at the current time from the terminal voltage, by storing a plurality of such maps corresponding to the plurality of charge currents, and by referring to the maps to acquire the remaining charge time corresponding to the SOC and the charge current (for example, see Japanese Patent Application Publication No. 2011-91879).
However, in the maps described above, the relationship shows a shorter remaining charge time as the charge current increases, and according to the calculation of the remaining charge time using the maps described above, when the charge current decreases during a charge process, as compared to the remaining charge time before the decrease in the charge current, the remaining charge time becomes longer. In other words, despite during charging, there is a problem that the calculated remaining charge time becomes longer.